Theoretical prediction of electronic properties and contact barriers in a metal/semiconductor NbS2/Janus MoSSe van der Waals heterostructure.

The emergence of van der Waals (vdW) heterostructures, which consist of vertically stacked two-dimensional (2D) materials held together by weak vdW interactions, has introduced an innovative avenue for tailoring nanoelectronic devices. In this study, we have theoretically designed a metal/semiconductor heterostructure composed of NbS2 and Janus MoSSe, and conducted a thorough investigation of its electronic properties and the formation of contact barriers through first-principles calculations. The effects of stacking configurations and the influence of external electric fields in enhancing the tunability of the NbS2/Janus MoSSe heterostructure are also explored. Our findings demonstrate that the NbS2/MoSSe heterostructure is not only structurally and thermally stable but also exfoliable, making it a promising candidate for experimental realization. In its ground state, this heterostructure exhibits p-type Schottky contacts characterized by small Schottky barriers and low tunneling barrier resistance, showing its considerable potential for utilization in electronic devices. Additionally, our findings reveal that the electronic properties, contact barriers and contact types of the NbS2/MoSSe heterostructure can be tuned by applying electric fields. A negative electric field leads to a conversion from a p-type Schottky contact to an n-type Schottky contact, whereas a positive electric field gives rise to a transformation from a Schottky into an ohmic contact. These insights offer valuable theoretical guidance for the practical utilization of the NbS2/MoSSe heterostructure in the development of next-generation electronic and optoelectronic devices.

A new approach for ultra-high adsorption of cationic methylene blue in a Zr-sulfonic-based metal-organic framework.

A series of Zr-sulfonic-based metal-organic frameworks have been synthesized by the solvothermal method, namely VNU-17 and VNU-23. Particularly, VNU-17 and VNU-23 adopt the sulfonate group (SO3 -) moieties densely packed within their structure, which can efficiently uptake MB+ from wastewater. The maximum adsorption capacity for MB+ onto VNU-23 is up to 1992 mg g-1 at pH = 7, which is more than five times that of activated carbon and possesses the highest value among all the reported MOF materials. In addition, VNU-23 retains the adsorption uptake of MB for at least five cycles. The adsorption isotherms and kinetic studies reveal that MB+ dye adsorption onto VNU-23 fits a Langmuir isotherm and the pseudo second order kinetic model. Furthermore, the ultra-high adsorption capacity of VNU-23 for MB dye can be accounted for by the suitable pore/channel size together with electrostatic attraction and π-π interactions. These results indicate that VNU-23 can be utilized as a promising candidate for removing MB+ from an aqueous medium.